Contrast control in video systems is achieved by increasing or diminishing the amplitude variation of the video signal to increase or decrease the contrast of the video image produced by the signal. One problem is that the video signal is supplied through a coaxial cable in most systems, and contrast control is provided by a variable resistor connected between the coaxial cable and the video system. As is well known in the art, unless the coaxial cable is terminated in its characteristic impedance, spurious reflections of the video signal will occur at the boundary between the coaxial cable and the video system to which it is attached. Thus, adjustment of the variable resistor in order to change the video contrast will necessarily change the impedance in which the coaxial cable is terminated, which may cause the spurious reflections of the video signal. If it is desired to control the video contrast at a location which is removed by a substantial distance from the termination of the coaxial cable at the input to the video system, the variable resistor must be installed at the distant location and the video signal must travel an additional length of cable corresponding to at least twice the distance between the video system input and the location of the variable resistor. The additional cable length represents an increased capacitance which impairs system performance, as is well known to those skilled in the art. This latter problem may be overcome by substituting a field effect transistor at the video system input for dividing the voltage of the video signal supplied to the video system across the source and drain of the transistor. The gate voltage of the field effect transistor may be varied by a variable dc voltage source at the distant location, thus permitting contrast control over a long distance without increasing the distance traveled by the video signal. However, it is not possible to vary the video contrast in a linear manner using a field effect transistor because the source to drain resistance of the field effect transistor is a nonlinear function of its gate voltage.